Carbon nanotubes (CNTs) are nanomaterials that individually include properties of high modulus, tensile strength, aspect ratio, and electrical and thermal conductivity. Early fabrication of CNT filaments was based on “wet” spinning methods, which require dispersing CNTs in a solution for further spinning processes. The chemical dispersion process generally leads to a low usage of CNTs, and the spun filament usually contains surfactants or polymer molecules which reduce the strength and the thermal and electrical properties of the filament. “Dry” spinning methods are also used to prepare CNT filaments composed of pure CNTs from as-grown super-aligned CNT (SACNT) arrays. More recently, the dry spinning method that directly spins CNT filaments from SACNT arrays has attracted attention because the dry spinning method is simple and controllable to produce continuous CNT filaments.
The dry spinning method is enabled by the van der Waals forces between CNTs that provide a cohesive force that enables the CNTs to readily stick to one another. While the van der Waals forces may be disadvantageous to applications such as composite films where a high degree of dispersion is preferred, the van der Waals forces can prove useful in the preparation of CNT filaments, threads, and ribbons. However, while the van der Waals forces are relatively strong in an orientation that adheres the CNTs to one another (i.e., in the thickness of the filament) the van der Waals forces are comparatively weak in an orientation of CNT alignment (i.e., along the length of the filament). Therefore, filaments made from CNTs typically exhibit tensile strength that is orders of magnitude less than the tensile strength of the individual CNTs. Accordingly, improvements in the strength of thread made from CNTs is desired.